Injection valves are in widespread use, in particular for internal combustion engines where they may be arranged in order to dose the fluid into an intake manifold of the internal combustion engine or directly into the combustion chamber of a cylinder of the internal combustion engine.
Injection valves are manufactured in various forms in order to satisfy the various needs for the various combustion engines. Therefore, for example, their length, their diameter and also various elements of the injection valve being responsible for the way the fluid is dosed may vary in a wide range. In addition to that, injection valves may accommodate an actuator for actuating a valve needle of the injection valve, which may, for example, be an electromagnetic actuator.
In order to enhance the combustion process in view of the creation of unwanted emissions, the respective injection valve may be suited to dose fluids under very high pressures. The pressures may be in case of a gasoline engine, for example, in the range of up to 200 bar and in the case of diesel engines in the range of up to 2000 bar.
After a desired injection during the injector closing phase a post injection can occur caused by an injector reopening. Current injector design includes very often a needle armature de-coupled feature. This design increases the impact between armature and upper armature retainer and also allows the needle to have the so called needle overshoot behavior. The needle overshoot happens during the injector standard operating mode: there is a needle overshoot during the needle opening phase. The needle overshoot during the opening phase occurs after that the armature impacts the pole piece impact face. When the armature stops and bounces against the pole piece impact face, the needle continues its motions by the effect of its inertia. By means of this phenomenon the opening phase is controlled for the armature but it is not controlled for the needle. Since the needle movement is responsible for fuel delivery, it happens that just at the end of the opening phase the needle is not in a controlled position in respect to the injector seat. This is unfavorable injector behavior and it impacts in particular way the minimum controllable deliverable flow. Due to the opening phase needle overshoot behavior, the minimum controllable flow quantity is increased. During the closing phase the armature overshoot occurs in the opposite direction, the armature detaches from the armature upper retainer and compresses the anti bounce spring eliminating the needle bounce at closing. Once that the anti bounce spring is compressed it releases the stored energy pushing again the armature against the upper armature retainer generating the unwanted and uncontrolled operating condition of the so called post injection.